The invention arose out of needs and concerns relating to open pit coal mining. Open pit mining commonly is performed using a combination of drilling and blasting techniques, and excavating machinery to remove material from the open pit. Excavating machinery is also used to break material away from upright faces of material for its subsequent removal from the mining pit. Such machinery typically includes a horizontally mounted, open cutting head having peripheral cutting elements such as teeth or buckets for braking material from the face.
Presently accepted machinery and methods have many drawbacks. For example, some excavating machinery is mounted on three or four track crawlers, requiring an inordinate amount of open pit area for maneuvering. Also, a number of excavators use bucket wheel cutting heads for breaking material from a face. These excavators rough cut a face of material, resulting in a significant loss of product from the face and requiring separate clean-up machines. Bucket wheel excavators are also limited in the hardness of the material that they can effectively remove.
Needs still remain for improved excavating machinery and methods which are capable of removing material from a tall face at high capacity rates. This invention is directed to improved capacity and other operating characteristics and methods in excavating tall faces of material, such as in open coal pit mining.